JFFS2 case insensitivity

[David Woodhouse]

On Tue, 2004-01-27 at 15:48 +0200, Jarkko Lavinen wrote:
> User space people want the file name case insensitivity.  I guess the
> old files are likely to be selected from a list on an embedded device.
> However case insensitivity is a desirable feature when adding new file
> names.

What do you mean, precisely? You're still describing the imagined
solution rather than the problem.

Case sensitivity is more clearly applicable in _lookup_ -- when trying
to find a given file from its name.

In the case of file _creation_, that affects the collision detection --
case insensitivity will usually cause you to be forbidden from creating
a new file with a name which differs from an existing name only in case.

Is that what they want it for? Why -- what is the real source of the
requirement?

> My primary concern was to estimate the cost or pain of implementing
> file name case insensitivity and find arguments against doing it in
> the kernel.

It is fairly painful -- you have to provide your own dentry_ops for
comparison and hashing, which mostly sorts out the evil dcache coherency
issues we used to have with case-insensitivity. 

But you still have to know the character set. That was vaguely OK for
FAT, where we had to play charset games anyway, but I _really_ don't
want to have the JFFS2 code play with character sets and know that û is
really the same as Û, etc. And don't get me started on Ŵ and ŵ :)

You really ought to be able to do this in userspace. 

-- 
dwmw2